Darren Burke, Communities reporter

A Sheffield medical expert says men can improve their sperm quality by wearing loose underwear and quitting smoking.

Allan Pacey, British Fertility Society spokesman and professor of andrology at the University of Sheffield, has issued the advice on the back of a new survey which revealed that men can also improve their sperm quality through exercise.

Running or jogging for up to 45 minutes during each training session may boost the volume of sperm as well as its motility and concentration in just a few months, according to new figures.

But Mr Pacey has said that links between sperm quality and exercise are unclear.

He said: "We have a very poor understanding of how physical exercise affects male fertility and sperm quality, but it is a question commonly asked by men wishing to improve their chances of having a child.

"We know at one end of the scale, men with sedentary lifestyles have poorer sperm quality than men who undertake regular exercise whereas, at the other end, we know that men who train very hard have poorer sperm quality than men who undertake moderate exercise. Therefore, there is probably a level of exercise associated with optimum levels of male fertility, although that is poorly defined."

Researchers found that jogging could improve the quality of sperm in men aged from 25 to 40.

The results of the study, published in the journal Reproduction, showed that men who exercised had improved sperm at the end of the training.

Added Professor Pacey: "In this context, the study makes a good contribution to the knowledge base. It is a very well conducted and a strength is that it is a randomised controlled trial with extensive data collection. Also, the study examines how exercise affects many of the parameters of male reproductive health, not just sperm quality.

"However, what is likely to be of most interest to men and their doctors are the results concerning sperm quality. Importantly, these seem to show a statistical improvement to various degrees when the men embarked on their different exercise regimes compared to men who did no exercise at all.

"However, an important question is whether these statistical changes are enough to be of any clinical significance. Unfortunately, this is questionable and it would need more research to be carried out to determine if men who exercised were more likely to become dads either naturally or with some form of assisted conception."

Dr Pacey said men could take other steps to boost their fertility and general health, including following a healthy diet, stopping smoking and wearing loose underwear.

Lead author of the study, Behzad Hajizadeh Maleki, said: "Our results show that doing exercise can be a simple, cheap and effective strategy for improving sperm quality in sedentary men.

"However, it's important to acknowledge that the reason some men can't have children isn't just based on their sperm count. Male infertility problems can be complex and changing lifestyles might not solve these cases easily."